Construction And Simulation Of Reconfigurable Photonic Crystal Valley Topology

In recent years,the analogy of quantum Hall effect,quantum Spin Hall effect and quantum Valley Hall effect with classical electromagnetic and acoustic systems has become an important research topic.They bring unique topological edge states,which can provide one-way backscattering free transmission and defect insensitive transmission advantages.Among them,quantum Valley Hall effect has been rapidly developed in the research field due to its flexibility and diversity,which lays a foundation for the construction of reconfigurable photonic crystal valley topology.In this thesis,a reconfigurable valley topology photonic crystal model is constructed using liquid crystal materials which can be regulated by voltage.In order to realize flexible and reconfigurable topological edge state waveguides,valley photonic crystals are constructed using liquid crystal filled rods.The permittivity of the two rods in one cell is determined by the external voltage,which makes the valley photonic crystal have different valley topological phases,thus reducing the rotational symmetry of its lattice.The vortex chirality of the photon energy flow provides a new degree of freedom for the light wave through the orbital angular momentum and the valley topological boundary state is obtained.The external voltage of the LCD is controlled by the "0" and "1" codes on the control panel.The topological edge states of reconfigurable and diversified transmission paths can be realized by programming,and the results are authenticated by field propagation simulation.In addition to the use of liquid crystal materials,a silicon dielectric column structure with three circular holes is also studied,which can be regulated by rotation to achieve valley topological boundary states.We constructed three equally sized circular holes in a silicon dielectric column and filled them with air.By rotating the column,the Dirac points are opened,and two nontrivial bandgaps and two-band valley topological boundary states are obtained.The spin-locked excitation depends on whether the non-trivial band gap is closed by a valley topology boundary state.Finally,the reconfigurability of the model is realized by using the idea of programmable coding,which provides a potential application prospect in photonic routing control of chip.In the application of reconfigurable valley topology photonic crystals,a beam separation structure is designed in this thesis.In this thesis,we construct a strong local beam separation model based on the protection ability of the valley topology corner state of photonic crystals.Fine-tuning of 1-2 dielectric columns in the base model by coding.Implement selective transmission of models up and down.By analyzing the S function related to the ratio of input and output ports,the transmission spectrum and transmission specific gravity are calculated,and the structural models with different spectral effects under different frequency selection are realized,which expands the design and application of optical devices.